1. Field of the Invention
The present invention relates generally to telecommunication systems and more generally to an automatic telephone dial-out voice notification system.
2. Description of the Background
Various types of message broadcast systems exist for broadcasting a message to a group of people. Public alerting refers to broadcasting an alert to a population within a geographic area, for example, all residences in a particular city. Emergency notification generally refers to messages sent to a specific list of recipients. This list may be further constrained, for example, to a geographical area. For example, an emergency notification may be sent to all Fire Department Chiefs within a city.
One type of message broadcast system is a dial-out voice notification system in which a computer server is used to deliver a pre-recorded voice message to a list of telephone numbers. These systems dial each number in the list and then play the pre-recorded message when the call has been answered. Multiple numbers may be dialed simultaneously, depending upon the number of ports available on the server. If there is no answer, the system moves on to the next number and will periodically re-try the no-answer telephone number. The system continues to dial the numbers until the message has been delivered to all numbers in the list (or until some time-out period has expired). Such systems may be used, for example, by governments in order to implement emergency notification systems or by corporations in order to implement broadcast messages to employees. These dial-out voice notification systems have the advantage of being able to deliver a large amount of message content. However, these systems also have the significant disadvantage of being very slow to deliver their messages and are thus often limited to using small contact lists in cases of time sensitive information.
Aside from the physical limitation of the number of ports that the server uses to connect to the telephone network, the delivery performance of dial-out voice notification systems is impacted by the time it takes to complete a call and the duration of the voice message. The call completion time is the sum of call setup time and the time it takes for a person to answer the call while it rings. Call setup time typically ranges from 3 to 5 seconds depending upon access facility and network response. Assuming that, on average, a call is answered after three ringing cycles (with a typical six second ringing cycle), the average time to answer a call is estimated at 18 seconds. With a 30 second voice message, it is seen that each call will last approximately 52 seconds (18+30+4). Thus, with even a fairly modest number of recipients, delivering messages in this manner can take hours, if not days.
Another problem with current dial-out voice notification systems is that upon answering such a call, a listener is likely to require several seconds to understand the nature of the call (since the receipt of a broadcast message may be unexpected), which may result in the listener missing part of the message. In order to deal with such situations, dial-out notification systems usually allow the user to request a replay of the message. While this aids in ensuring that listeners understand the message, this extends the call duration and further delays delivery of the message to all intended recipients. For example, if the listener requests a message to be replayed, the call duration now becomes 82 seconds (18+30+4+30), limiting each server port to no more than 43 calls per hour.
Answering machines pose additional difficulty for dial-out systems. First, answering machines are usually configured to be the device of last resort to answer an incoming call. In this environment, answering machines are generally set to pick up after 5 ringing cycles. Whereas the previous examples used 3 ringing cycles on average, the extension to 5 ringing cycles adds another 12 seconds to the call duration. Second, when the answering machine picks up, it begins to play a greeting that may last for 5 to 10 seconds before beginning to record, thus adding additional time to the call duration. Third, when an answering machine picks up, dial-out servers experience difficulty in determining whether they are communicating with a person or another machine. If the dial-out server falsely believes it is communicating with a person, it may begin to play the message before the recording starts. As a result, the initial part of the message, which most likely identifies the nature of the emergency, may not be recorded. If the dial-out server determines correctly that it is communicating with another machine, it may still incorrectly detect the moment that recording begins because answering machines do not all use the same prompt tone, if any at all. One solution to this problem is to automatically repeat the message resulting in a 94 second call (30+30+4+30).
Further, in situations where the call is not answered, the server must periodically re-try no answer telephone numbers. Each no-answer attempt will consume an additional 34 seconds (30+4), assuming the server abandons the attempt after 5 rings. If 30% of the telephone numbers result in no answer on their first attempt, the average call duration is extended by about 20%. Statistics from commercial dial-out services confirm that no-answer calls, busy lines and answering machines prominently degrade call throughput. Thus, as can be seen, while current dial-out voice notification systems allow for the delivery of a large amount of message content, several limitations may make them too slow for many time sensitive applications.
One system for addressing the speed issues of the dial-out notification systems is described in U.S. Pat. No. 6,021,177, which describes an alarm/notification device that connects to a telephone line and monitors the telephone line for a specific alarm signal. When the special signal is received, the device responds with a visual and/or audible notification. The visual notification may include an LCD for displaying a short text message. An advantage to this type of system is its speed. This type of system can send messages to homes much more quickly than the above described dial-out voice notification systems. However, the trade-off for speed is the lack of significant message content. The text message of this type of system is limited to a relatively small number of characters (typically 10 to 60), and therefore this system cannot deliver the extensive message content of the dial-out voice notification systems.
As can be seen, the current message broadcast systems must make a trade-off between content and speed. The dial-out voice notification systems are able to deliver a large amount of content but are very slow to deliver such content to even a moderately large recipient population. The system described in U.S. Pat. No. 6,021,177 is able to deliver its content quickly but is significantly limited in the amount of content it can deliver.
Therefore, there is a need for a message broadcast system that can more quickly deliver a large amount of content.